irregular implies deviation from the customary or established rule, procedure, etc. irregular conduct; abnormal and anomalous imply deviation from the normal condition or from the ordinary type, abnormal stressing atypical form or character a man of abnormal height, and anomalous, stressing an exceptional condition or circumstance in the anomalous position of a leader without followers; unnatural applies to that which is contrary to the order of nature or to natural laws an unnatural appetite for chalk